Counter Strike: Source - Game caps FPS at ~20?

I've been playing CSS for while on this machine (almost a year now). And for some reason, it has started to act weirdly.
About a week ago, whenever I am playing CS:S the FPS will cap at 20fps for about a round or two. This makes it very difficult to play. I usually get from 50-60fps.
I have updated my video drivers and changed back to my Omega drivers (which I have always had luck with). I did everything that the Steam support page mentioned about "In-game video lags".
Specs, if they are useful:
Intel Pentium D 3.2Ghz
1 GB DDR2 Kingston RAM
ATI X1600PRO

Ok, well... No one answered.
But, I found out that whenever the CPU temperture hit ~60-69C it started lagging like this. (Sticking around 3-20 FPS)
Strange because on idle it runs 35-40C

I cleared up the area around the heatsink (moved cables around) and opened up the side panel. The temperatures during the game were 50-55C
I looked under the OC'ing section and it said 60 or less is safe.

But how did the temperature of the CPU effect the FPS?

And its strange how this only started happening recently, I've been playing CSS for almost two years now (1 on this machine).

One other question: Does upgrading your RAM put more pressure on your processor? That may be why it wasn't affecting my game before because I recently upgraded from DDR to DDR2 533Mhz.

Oh yes, and during the game the GPU runs at about 53-59C and idle about 38-42. It's an ATI X1600Pro

One more thing, both the GPU and CPU do NOT have stock coolers.
Thanks

If the CPU is overheating, it will automatically slow down to protect itself. The slowdown will tend to cool it somewhat.

You might want to clean any dust buildup on the heatsink fins and fan if you haven't already. It might be that the thermal compound between the heatsink and CPU is hardening or breaking down. Removal of the heatsink, a thorough cleaning of the contact surfaces and reapplication of fresh Arctic Silver or similar thermal compound might do the trick.

If the CPU is overheating, it will automatically slow down to protect itself. The slowdown will tend to cool it somewhat.

You might want to clean any dust buildup on the heatsink fins and fan if you haven't already. It might be that the thermal compound between the heatsink and CPU is hardening or breaking down. Removal of the heatsink, a thorough cleaning of the contact surfaces and reapplication of fresh Arctic Silver or similar thermal compound might do the trick.

Click to expand...

Alright! Thanks
I haven't had much luck working with thermal paste, but I'll try again...

I have the same problem as him, I downloaded SpeedFan and found out the problem was the CPU was constant at 60c ( which is really crazy high, about 160f ) so what I did was take off the fan and replaced it with another CPU fan ( just bought one at BestBuy, didn't feel like waiting a week for newegg ) and replaced the compound with ArticSilver 5 and now it's to 45c, it doesn't slow down any more

Well I figured the problem is the warm CPU. When it reaches 60+C it starts slowing down too cool itself down. Thats the only possible explanation, since when I take off the side panel this lag never happens.

I guess I need to change my heatsink or something, but first I'm going to apply a new layer of thermal grease to see if that helps.

Although a autoexec.cfg script could help, this isn't the case... It's because his CPU was overheating ( as he said was 60c which is about 170f ) which would cause the motherboard to automatically switch to "ZOMGWTFBBQ!" mode to protect the CPU from getting any higher... which could kill it